SALT-BUSH IN THE HEART OF THE SAHARA KILLED OUT BY CHOKING SANDS
DISINTEGRATING ROCK IN A REGION OF TASSILI
Again, in a further paper in Novitates Zoologicæ, March 1924, dealing with my second expedition, Dr. Hartert adds:
“More than ever it is clear that the ornis of Aïr is tropical, as a country where Sunbirds, Barbets, Glossy Starlings, etc., live has a tropical ornis, though there are a number of palæarctic species, to which now a few must be added. On the other hand, these striking tropical families like Sunbirds, Glossy Starlings, Emerald Cuckoos, Hornbills, Barbets, are absent from the Ahaggar (Hoggar) Mountains, and the almost lifeless desert between Aïr and Ahaggar forms the boundary between the palæarctic and tropical African faunas.”
From all this it is clear that Aïr maintains many tropical influences that penetrate northward, like a wedge, far into the Sahara, although its surroundings are foreign to like conditions. For instance, regarding the last remark, if we draw longitudinal lines 200 miles or so clear of either side of the Aïr Mountains, immediately those lines leave the southern shores of the Sahara, about latitude 15°, they enter desert where all tropical influence ceases.
A DESERTED STONE-BUILT VILLAGE OF AÏR
If we ponder over the thought that the Sahara is increasing in sand, and size, is it not conceivable that this mountainland of Aïr is as an island that, because of its altitude, is left high and dry out in the open while the plains surrounding it have been gradually smitten as by a plague that has slowly driven back the line of fertility, while that which remains, as representative of a configuration of the past, is the rugged rock land that still offers a bold front to the advances of time and decay?
I am confident that therein lies the truth—that formerly a wide pre-Saharan region of fertility once reached much farther north than at present; and, when it became flooded over with rising sand, and lost, Aïr still remained, and, behind the shelter of its rocks, retained a good deal of its old characteristics. All around the Sahara I believe that conditions of a similar nature exist.